The purpose of this trial was to determine how well a neural
network would respond to a recording of a mimicked vocalization. Starlings have
a wide range of vocalizations including those learned from other birds. Among
the vocalizations commonly mimicked by the Starling are those of large birds of
prey. It is thought that they do this in order to scare other small birds
away from their territories. The basic network was built and trained against
both European Starlings own vocalizations and those of Bald Eagles. The network
perfectly classified both calls when tested. Finally, a recording of a Starling
mimicking the Bald Eagle call used for training was passed into the network. The
following figure shows the frequency spectrum of typical Starling and Bald Eagle
vocalizations as well as that of the mimicked vocalization passed into the
network.

While the network classified the mimicked vocalization as a
Bald Eagle in almost all networks built, the numeric result produced showed that
the decision was a close one. While the typical Starling and Eagle vocalizations
were given values close to one for the correct category, and values close to
zero for the incorrect category, the mimicked vocalization was given a value
between 0.5 and 0.6 for the Eagle category and 0.4 to 0.5 for the Starling
category in most cases. This shows that, while the network could not classify
the mimic as a Starling, it didn't fit the classification of Eagle much better.